Amazon Software Development Engineer interview questions

The first round was a written technical and intelligence test. Second round was a coding round where two questions were related to BST and one related to Strings. The interview were held on next day for the 30 shortlisted candidates out of 300 odd who attended the initial rounds. The first interview began with questions from the code I had written in the second round. Was asked to optimize it, and explain the code (draw recursion stacks and explain how hashset works were auxillary questions asked as I was explaining my code). If you get stuck, they do give you a hint. But one hint per interview is the max you can expect. Duration: 45mins. Second interview was held 3 hours after the first one. And this one was with a Development Lead. I guess this was a bar raiser for me, a concept unique to Amazon. This interview can be difficult or easy depending on what kind of projects you've done, what kind of activities you engage in. Typically, this round assesses your overall qualities, and assesses if you're fit to work for Amazon.com. Was a really long interview, about 2 and half hours. Third interview was again on algorithms and data structures. I was asked an odd question regarding race condition, and synchronized blocks in java. I was given no hints in this round, although I eventually managed to answer all the questions he asked. Duration: 1hour 15mins. Foruth interview was with a senior developer at Amazon.com. He asked four questions, and told me to write my best code for each, with utmost optimization. He told me I can take all the time in the world to solve the problems. Each one was algorithm based. After I had answered all the four, I walked him through all the test cases. Later he asked a question from Probablity, which I struggled to answer, but I guess it didn't matter as my performances in the previous rounds were excellent.

I was contacted by an Amazon.com recruiter without me applying for any position. I assume they found me at Dice.com. I set up a phone interview with the recruiter and scheduled it for later in the week. The interviewer opened with information about what they were looking for, a generalist programmer basically, then asked if I had any questions for him, I did but he couldn't answer them very well since he is not on the team that the job is for. Then he went into questions, first he asked me about garbage collection, I think he was looking for how it works at a low level, but wanted a very general answer. Next he asked about how browsers and the internet work, again very general answer. The programming problem dealt with looking for substrings without using high level language methods, I'll post that question. Then he gave me another chance for questions. About half a week later I was contacted for a second phone interview (they said there could be up to 3 phone interviews) which is scheduled for later this week.